Among bearings for open-end spinning rotors, apart from the bearing in a supporting disk wedge slit, contactless bearings such as magnetic bearings and air bearings have also become known. Usually, rotors mounted in this way are electric motor driven by an individual drive. The rotor housing, which is under negative pressure during operation, is closed with a detachable lid to allow access to the rotor housing under certain situations. For example, if spinning is interrupted because a thread break or a cleaning step requires the opening of the rotor housing to perform maintenance work. Sometimes operating staff must open the rotor housing during continuous operation as well. On the other hand, the bearing and drive are arranged in a drive housing largely separated from the rotor housing, first of all to keep the volume of the rotor housing to be impinged with negative pressure small, and secondly to protect the drive and bearing of the spinning rotor from dirt (i.e. dust and fiber fly). Owing to the very high revolutions per minute of the rotating spinning rotor, it is not possible to seal the rotor housing to the drive housing completely, so that a negative pressure starts building up inside the drive housing too during the spinning operation. For example, EP 1 156 142 B1 shows an open-end spinning device with such an individually driven and magnetically mounted spinning rotor.
If the rotor housing under negative pressure of such an open-end spinning device is now opened, pressure compensation occurs, while negative pressure still prevails in the contiguous drive housing. Because of this, dirt that had accumulated in the rotor housing can now be sucked into the drive housing when the rotor housing is opened. If this dirt now reaches all the way to the individual drive of the spinning rotor and to the bearing, it can cause the failure of the bearing and drive.
EP 2 069 562 A1 therefore suggests to provide the drive housing with an additional air inlet and to supply compressed air to the drive housing before the rotor housing is opened so pressure compensation can take place there even before the rotor housing is opened. As a result of this, no dirt is sucked into when the rotor housing is opened.